1. Field of the Invention
The present invention relates to a method for in situ renovation of underground tanks or wells, especially sewer manholes, where a prefabricated liner of reinforced plastic is inserted inside the well.
2. Description of the Prior Art
It is commonly known to perform renovation in situ of underground pipelines, e.g., sewer conduits, by means of a thermosetting polyester impregnated tubular stocking, which is made to fit by a longitudinal seam according to a specific task, and which then is turned into location by a special turning technique by means of water pressure for subsequent setting by supplying hot water. Furthermore, to a lesser extent it is known to use such an in situ renovation technique for renovating vertical tubular shafts in buildings, for example, ventilation ducts or refuse chutes.
However, so far it has not been known to use a corresponding technique for more voluminous vertical shafts such as transition wells which normally consist of a conical transition from 600 mm to 1000 mm, concrete rings with internal diameter of 1000 mm at a depth of about 1 to 4 m, depending on installation and a bottom section where inlet and outlet conduits and possible influx are joined. The bottom section is furthermore usually shaped with berms for obtaining an optimum sewage water flow in the well. The transition wells are located in the sewer network at a distance of about 50 m separation, and the transition wells are used for inspection, cleaning and the like. Furthermore, transition wells are also established where several sewer conduits are joined into a main conduit, or where there is inlet to a main conduit. A relatively large part of the many existing transition wells for example in Denmark need replacement within the next 10 years at a rate of several thousand wells per year. The wells often lie in the roadway, which means that the cost of digging up and lowering into position of a new well will run up to about 50,000 DKK per well, and to this is added very great traffic inconveniences in the surroundings. It is expected that the problem has the same magnitude in other countries.
The invention provides a method of the kind mentioned in the description of the prior art for in site renovation of transition wells, and which can result in a considerable economic saving and a considerable reduction of the negative implications of renovation.
The method according to the invention uses a liner in the form of a glass fiber reinforced stocking of thermosetting polyester or epoxy formed on a rubber coated mold by winding, weaving or braiding, the liner being designed in such a way that the length/diameter ratio of the liner subsequently may be changed by changing the angle of inclination of the glass fibers relative to the longitudinal axis of the liner, that is, adjusting the cross-section of the liner and simultaneous by adjusting the length of the liner.
By the above method it is possible to perform in situ renovation of underground manholes, for example, transition wells, with simple measures and without the negative traffic implications. According to the invention, the renovation may furthermore be performed relatively quickly and without real digging work which is considerably cheaper than a prior art renovation with replacement of a defective manhole. In terms of personnel, a considerable savings as a team of two or three persons may be counted on to renovate several manholes per working day, thus furthermore avoiding a long-term disruption of the sewer conduit.
Furthermore, a very optimal utilization of the composite materials of the liner, glass fibers and thermosetting plastic (polyester or epoxy), is achieved where the single glass fibers are bonded together in such a way that by a wall thickness of 6-8 mm there is achieved a compression strength corresponding to the compression strength of a known plastic impregnated felt stocking with a wall thickness of about 20 mm.
Suitably, the method according to the invention may be thus modified, so that there is used a liner in the shape of a glass fiber reinforced stocking of thermosetting polyester or epoxy formed by winding, weaving or braiding externally of a unilaterally suspended, rubber coated mold with a diameter allowing the mold to be lowered through a sewer manhole curb or cone, i.e., with a diameter of the magnitude of 500-900 mm, the rubber coating consisting of a detachable rubber bag that may be expanded by a factor of about 3, and which is preferably fastened to a flange that may be displaced externally of the mold, the polyester or epoxy liner being wound at an angle of about 15-20xc2x0 relative to the longitudinal direction of the mold in such a way that the length/diameter ratio of the liner may subsequently be changed by changing the angle of inclination of the glass fibers up to about 120xc2x0 relative to the longitudinal direction as the polyester or epoxy impregnated glass fibers are connected with the flange by the winding, weaving or braiding. The prefabricated liner may optionally finally be covered by winding with, e.g., polyethylene film for possible cool storage until mounting in the well.
Preferably, the renovation of a manhole by the method according to the invention takes place in such a way that the mold with the closed end of the stocking shaped, glass fiber reinforced polyester or epoxy liner is lowered into the manhole, pressure is supplied between rubber bag and mold, preferably by filling with water so that the liner expands and assumes the shape of the internal surface of the manhole simultaneously with the external flange being allowed to be displaced downward so that the angle of inclination of the glass fiber winding is allowed to increase at the expansion of the liner, and, when the liner has conformed to the internal surface of the manhole, hot water is supplied between mold and rubber bag so that the polyester or epoxy liner sets. Surprisingly, it has been discovered that the polyester or epoxy liner expands rather easily in response to the water pressure and conforms to possible unevenness at the inner side of the well, so that by the subsequent setting of the liner a smooth new, easy-to-clean surface is formed which furthermore may resist attack from chemicals occurring in sewage water.
If considered necessary, the method according to the invention may be further modified by the winding with polyester or epoxy impregnated glass fiber being combined with cutter glass of a length about 25 mm, and optionally include upifila mat.
In addition, the invention is a prefabricated liner for in situ renovation of wells, especially transition wells, the liner comprising polyester or epoxy impregnated glass fibers, the liner being formed with a wall thickness of 5-10 mm, preferably about 7-8 mm, by winding on a mainly horizontal, unilaterally and rotatably suspended, tubular mold with a diameter of about 500 mm, a length of about 6000 mm and a domed bottom with a center support opposite to the rotary suspension, the tubular mold being covered by a detachable rubber bag prior to the winding, where the bag may expand by a factor of about 3 and is fastened to a flange situated close to the rotary suspension and which may be displaced externally of the tubular mold, and which is connected with the glass fibers.
In order to achieve a smooth inner side wall of the liner, the rubber bag is surrounded by a polyethylene film prior to the winding with polyester or epoxy impregnated glass fibers.
With the purpose of further reinforcing the liner according to the invention, the winding with polyester or epoxy impregnated glass fibers may be combined with cutter glass of a length about 25 mm, and optionally include unifila mat.